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Discussion Starter · #1 ·
I am trying to get my 01 F4i's suspension setup better and need some help. I have no idea what the sag numbers should be. I weigh 150-155. I like my suspension set fairly stiff and have been riding it with 3 lines preload on the front, and on setting 5 on the back. I like the way that it turns in with this setup but it rides harsh. I recently went to setting 4 out back and 1/2 turn more comp damping.

anyone have any suggestions?
thanks

redCBR


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Dude, I have been neck deep in the suspension stuff for the past week. I'm actually getting dumber, I think. Anyway, I'm not going to type out everything, so just go check this out. Great info and troubleshooting for your suspension settings.

http://www.circuit1.com/circuitone_tuneguide.html

Good info - I just set my sag and wrote down my settings for track day on Monday. We'll see how it goes. BTW - on your shock preload setting - what is the reference point on the shock as to which position you have set? Is there one? Like, how do you know you're in position "X"?


PS - You'll definately need help getting your sag numbers. The ones listed are for you sitting on the bike. If you want a good how-to for setting sag, check in the tech forum (I think) back a ways and I posted a question about it. Got a good answer, too.

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Are you using stock suspension or aftermarket? Idealy for aftermarket sag numbers is usually 30mm. Sounds like you need to mess with your rebound and compression. Rebound needs to be quick so you need to fix that. So if you push down on the front forks they should bounce back up quickly but not settle back down, they should come up and stop. If your getting hardness thru bumps you need to adjust your compression to absorb the bump. Aftermarket fork internals will really help you out there. Then basically adjust the rear much like the front test I just mentioned. If you have to much rebound in the rear you'll spin the tire so watch out how much you add. The rear can rebound a bit slower then the front, but no longer then a second for it to rebound. Good luck. You can change your geometry of the bike also if you lower the front which will help it steer in quicker, but to low and the bike become unstable, your kinda suckin for raising the rear any unless you can machine up a spacer to add under your stock shock mount to the frame bar.
 

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Discussion Starter · #4 ·
I am using stock suspension for right now. I will probably upgrade the forks in a few months with racetech stuff. The front end is pretty harsh so i think i will put the preload back to stock and mess with compression and rebound like you said.
thanks,

redCBR


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Yeah, what F4iRcaer said... /images/icons/wink.gif Another way to lower the front is to slide the fork tubes up about 5mm in the triple trees. There is a good how-to article in a recent bike rag (SR or MC - can't remember) on how to do just that. I have decided to keep my F4i and my next purchase will be (probably) Traxxion Dynamics or (maybe) RaceTech fork springs. I'm a big fella, and the stock springs just aren't cutting it. I'm thinking valving too, but the budget has to agree. I've talked the subject up with some folks and the consensus seems to be that 10wt oils and 1.0 springs should make a big difference for me, even with the stock valving. When I start racing, I'll send my forks to Max at Traxxion and let him work some magic with the valves.

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<blockquote><font size=1>In reply to:</font><hr>

Another way to lower the front is to slide the fork tubes up about 5mm in the triple trees.

<hr></blockquote>

What do you mean "another way"? That is THE way(well, the mm can vary).
You will get better results from raising the rear as F4iRacer suggests though. It is not at all hard to make a spacer to fit. Just get a 3/8 inch or so thick piece of aluminum and drill a hole in the center of it and put it between the top of the shock and the frame. (unless you're short, then you might want to lower the front end instead)

 

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Raise the rear, lower the front - looking for the same result. Higher ride height and changing steering geometry. He mentioned raising the rear and that it could be a pain on the F4i. I think adjusting the fork tubes would be easier.

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Discussion Starter · #8 ·
Okay i put fork preload back to 3 lines, and raised comp. damping 1/2 turn. The front seems much better but i have not had a chance to ride hard to really test yet. Right now from the little bit i have ridden it i think it will need slightly more rebound damping on the forks. Once i get the feel i want out of the suspension i will probably drop the forks in the clamp by 5mm as suggested. So far it feels much better though. I havent had time to get the sag set quite yet, but maybe this weekend i will have time.

redCBR


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Lowering the front will help the bike turn in quicker but to much the bike will become unstable since your actually shortening your wheel base. I wouldn't go any lower then 10-15mm total in the front. At those numbers you'll be turning in really quick with minimal force on the bars but in return your bike will steer towards the apex to much and you have a better chance of highsiding cuz the rear will want to come around on you. It will also effect your heavy braking, to low in the front will make the rear want to swing around one way or the other. So just play with 5mm at a time in the front. If your getting to the point where you are having to fine tune your suspension and you still need more adjustment your going to HAVE to look into getting some aftermarket suspension. Now one thing you probably haven't thought about here is tires! As your tires wear down your suspension won't feel right anymore, don't adjust your suspension to fit worn tires! Sounds like you may want to look into getting some aftermarket suspension and start doing some trackdays and ride a bit slower on the street before it bites ya. I know from experience cuz it's happened to me. I no longer ride on the street cuz I was going to fast for street conditions, it's much safer to ride that fast on the track! So start looking into getting your forks done first (springs, rebound/compression valves), then look at either having your stock suspension resprung and revalved or look at a Fox shock they are a lot cheaper then say a Penske or an Ohlins. Good luck
 

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Suspension for dummies! Like me.

I found this on a message board and it's really good description of suspension set up. Enjoy.

Suspension for dummies

Actually, the subject line would be a good title for one of those books! There's a lot of misunderstanding about suspension.

I'll try to explain some things, since the question was asked kind of gererally.

The suspension is a spring. That's pretty much it. Really. So, why the he!! are there so many adjustments if it's a simple spring? Well, the spring will store energy (say after going over a bump), and if it's left alone, that spring will return that energy back to the bike. Pretty soon, you'll have a bike that's oscillating up and down like a couple of teenagers having sex for the first time. That's a lot of up and down!

So, to prevent the oscillations, engineers put in things call dampers. The dampers are a way of dissipating the stored energy of the spring. The dampers work by forcing oil through a small hole. The oil resists flowing through the hole, and bingo, you've got something to kill the oscillations (bummer for the two teenagers).

There are two sets of dampers on a CBR suspension system. There is a COMPRESSION damper and a REBOUND damper. Note that dampers only work in ONE direction. That's why there are two of them - to control the spring in up AND down motion.

The compression damper slows the compression of the spring. So, for the front fork the compression damper will slow the rate at which the front for compresses, like when under braking.

The rebound damper works in the other direction. When the spring unloads (springs back to normal length) then the rebound damper kicks in to slow down that motion.

For the front forks, the compression damper is a little screw located on the lower fork leg, just below the caliper brake mount. The rebound damper adjustment is on the upper end of the fork cap, in the center.

Adjustment directions are in the maual, but here's how to do it: using a screw driver, turn the adjustment screw clockwise, counting the number of turns, untill the screw seats lightly. DON'T FORCE IT! Remember the number of turns as this was the setting. Note that when the screw is fully seated, you have MAXIMUM damping. Now turn the screw counter clockwise to the desired setting. The stock setting for the CBR600 is 1 1/4 turns out from max for the compression damper.

The rear shock compression damper is located on the remote reservoir, which is attached to the left side of the rear sub-frame. The rear shock rebound damper is at the base of the shock body, looking from the right side. Again, see the manual for more info.

Now for the preload! Preload is exactly what it means - you're 'preloading' the spring. Here's how it works: there is a spacer on placed on inside the fork tube, on the top of the spring which has a threaded adjustment on it. That the thing you see at the top of the fork cap. By turning the preload clockwise - your pre-compressing the spring. If you turn it counter clockwise, you un-compressing the spring.

What happens is that the moment you sit on the bike, you add a load which the spring has to balance. If you PRELOAD the spring a lot, then the spring will not move very much when you sit on it. It doesn't need to travel very much to balance the load (your weight).

If you lightly preload the spring, it will compress a LOT to balance the load. The amount of travel the suspension goes through when you sit on it is called SAG.

The preload should be adjusted to an INDIVIDUAL RIDER'S WEIGHT. The optimum sag is ~25-35mm. Preload should be adjusted to get the optimum sag. That way the suspension is right in it's sweet spot, and the bike geometry is at its optimum. Guy's talk about the number of lines showing on the front fork cap as a measure of how much preload they have dialed in. Note that MORE IS NOT BETTER! It's a personalized adjustment.

IMPORTANT: Preload does not have any effect on the 'stiffness' of the spring. You can't make the spring stiffer with preload. The spring stiffness is solely a function of the spring rate (or spring constant).

As for the rebound setting, most guys like to set the rebound so that the bike will rise then settle slightly. Just push the front end down, and watch the motion as it comes back. It should rise at a nice rate, then settle back. The same goes for the rear, but the rise rate is usually a bit slower.

As for the right compression damping setting. Well there is no way to check that on a stationary bike. You just can't physically compress the suspension fast enough to get it to work. You'll have to go by feel. Start with the factory setting and ride it a while, then make a SMALL change. Remember to turn the set screw all the way in and count the number of turns as you go out (counter clockwise). That way you always measure from the same reference point.

Well, that got a lot longer than I thought it would. If you're confused, don't worry. It's not going to throw you off the bike. Just make small adjustments, try to record what you did, and have fun. And don't be afraid to ask someone for help. Racers are a good source. These guys are constantly working on suspension settings.



 

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Re: Suspension for dummies! Like me.

do this once you won't ever change it:
in the front;
rebound max minus 1
compression max minus 1
2 lines preload

on the back;
preload 4
damping max minus 1.25
compression max minus 1.25

these settings will make that squishy axz bike a rocket
but won't kill you on train tracks



............TWIST WITH AUTHORITIE............


 
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